In spaces having a working area common to both an industrial machine such as a robot, and a human, measures to ensure the safety of the operator are extremely important.
In this respect, article 150 paragraph 4 of the Japanese Industrial Safety and Health Regulations requires an industrial robot to be surrounded by a safety fence.
In carrying out work operations with a robot however, the work to be processed must be brought in to the movable part of the robot, that is to say into the operating region of the robot arm.
In the case of an operating system wherein the work is brought in by a human, operator safety is normally ensured by adopting a system wherein a door is provided at the entrance/exit of the safety fence. When the door is opened for work to be brought in by a human, the drive power source for the robot arm is switched off.
With large factories however, in order to rationalize the manufacturing process and improve efficiency, many robots surrounded by safety fences are arranged along the work conveying path, and automation of the manufacturing process is achieved by automatic conveying of the work and continuous processing. With this type of operating system wherein the work is conveyed automatically, it is difficult to provide a door to the entrance/exit of the safety fence. In such a situation, a system has been considered (U.S. Pat. No. 4,309,696) wherein sensors and the like are provided at the entrance/exit of the safety fence so that if a person passes through the entrance/exit, this is detected by the sensor. Judgement is thus made that someone is inside the safety fence, so that the drive power source for the arm of the robot inside the safety fence is switched off.
However at this time, it is necessary to reliably discriminate between work which is being automatically conveyed in succession through the entrance/exit, and a human, and to keep the drive power source for the arm of the robot on when work is being conveyed, to avoid a drop in work efficiency, and to reliably turn off the drive power source of the robot arm when a human enters, to maintain human safety.
In view of the above problems, it is an object of the present invention to provide a safety apparatus whereby, when a human enters inside a safety fence surrounding industrial machinery, the power source to the movable portion of the machine can be reliably stopped, while when a work piece is conveyed inside the safety fence, the power source to the movable portion of the machine is not stopped.